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JavaScript - replace last 4 characters in string

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Created by:
mkrieger1
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In this article, we're going to have a look at how to replace last 4 characters from string in JavaScript.

1. String slice() method example

This approach allows to get substring by using negative indexes. So by using 0 and -4 indexes as range we get <0, text.length - 4> text range. Then, we add the replacement at the end of the result string to replace the missing four characters.

// ONLINE-RUNNER:browser;

let text = 'ABCDE';
let replacement = '1234';
let result = text.slice(0, -4) + replacement;

console.log(result); // A1234

2. String substring() method example

This is alternative approach to slice method based solution. We remove the last 4 characters to add the replacement at the end of the result string to replace the missing four characters.

// ONLINE-RUNNER:browser;

let text = 'ABCDE';
let replacement = '1234';
let result = text.substring(0, text.length - 4) + replacement;

console.log(result); // A1234

3. String replace() method example

There is another trick that allows to replace all characters that match rexpression condition with an empty string. By using .{0,4}$ pattern we match any 4 characters (up to 4 characters) that are loacated at the end of string. Then, we add the replacement at the end of the result string to replace the missing four characters.

// ONLINE-RUNNER:browser;

let text = 'ABCDE';
let replacement = '1234';
let result = text.replace(/.{0,4}$/, '') + replacement;

console.log(result); // A1234

JavaScript - String (popular problems)

JavaScript - replace last 4 characters in string
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